Method for signalling different header information

ABSTRACT

The invention proposes a method for signaling various header data ( 5, 10, 20, 25 ) in the transmission of packet data units ( 1 ) in a telecommunications network depending on a type of the respective header data ( 5, 10, 20, 25 ), which requires the lowest possible bandwidth and bit rate. A set of header data ( 5, 10, 20, 25 ) received in a receiver ( 70 ) of the telecommunications network, depending on its signaling ( 30, 35, 40 ), is supplied to one of at least two groups ( 50, 55 ) of algorithms for an evaluation. For a first type of header data ( 5, 10, 20, 25 ), a first algorithm is provided in a first group ( 50 ) of algorithms, and for a second type of header data ( 5, 10, 20, 25 ) a second algorithm is provided in a second group ( 55 ) of algorithms, wherein the first algorithm corresponds to the second algorithm. The signaling ( 30, 35, 40 ) for the first type of header data ( 5, 10, 20, 25 ) and the signaling ( 30, 35, 40 ) for the second type of header data ( 5, 10, 20, 25 ) are combined into a shared signaling.

PRIOR ART

[0001] The invention is based on a method for signaling various headerdata according to the preamble to the main claim.

[0002] In packet switched telecommunications networks, payload data aretransmitted from a sender to a receiver in packet data units. The packetdata units pass through a number of protocol layers in the sender beforethey are finally sent to the receiver via the telecommunicationsnetwork. In the process, the individual protocol layers add header datain the form of so-called protocol control data to the actual payloaddata. These data are also referred to as “headers”. The header data withthe protocol control data and the payload data then respectivelycomprise a packet data unit. In this connection, the protocol controldata are used for example to convey the respective packet data unit withthe payload data through the telecommunications network to the receiver.As a result, an on the whole relatively large quantity of data can becombined for the protocol control data, which also have to betransported along with the payload data. Particularly in systems withlimited bandwidth, as is the case, for example, in mobile radio systemsor in telecommunication connections via modems, this especially impedesthe bit rate available for the transmission of the payload data.

[0003] Compression algorithms are used to reduce the data quantity ofthe protocol control data. These compression algorithms are known, forexample, from the documents RFC 1144, Compressing TCP/IP Headers forLow-Speed Serial Links (D1), RFC 2507, IP Header Compression, M.Degermark, B. Nordgren, S. Pink (D2), and RFC 2508, CompressingIP/UDP/RTP Headers for Low-Speed Serial Links (D3). Reference D2 hasdisclosed a first group of compression and decompression algorithms ofIP headers (Internet Protocol) in combination with TCP headers(Transport Control Protocol) and UDP headers (User Dataframe Protocol).Reference D3 has disclosed a second group of compression anddecompression algorithms, which are based on the compression anddecompression algorithms described in reference D2, but are only usedfor IP/UDP/RTP headers (RTP=Real Time Protocol). If packet data unitsare transmitted from a sender that contains a compressor, to a receiverthat contains a decompressor, then the decompressor must be notified asto the nature or type of header data that it is currently receiving.This is usually assured through a corresponding signaling in the form ofadditional data, as described in the specification “Subnetwork DependentConvergence Protocol (SNDCP)”, which are sent to the receiver along withthe corresponding packet data unit. In this case, for some types ofheader data with different signaling, a first decompression algorithm isprovided in the first group of algorithms and a second decompressionalgorithm is provided in the second group of algorithms, where the firstdecompression algorithm and the second decompression algorithmcorrespond to each other.

ADVANTAGES OF THE INVENTION

[0004] The method according to the invention, with the features of themain claim, has the advantage over the prior art that for the case inwhich, for a first type of header data, a first algorithm is provided ina first group of algorithms and for a second type of header data, asecond algorithm is provided, in a second group of algorithms, where thefirst algorithm corresponds to the second algorithm, the signaling forthe first type of header data and the signaling for the second type ofheader data are combined into a shared signaling. In this manner, thedata quantity to be transmitted in order to send the signaling alongwith the corresponding packet data unit can be reduced so that the bitrate for the transmission of payload data is impeded as little aspossible by the transmission of the signaling.

[0005] Advantageous modifications and improvements of the methoddisclosed in the main claim are possible by means of the measures takenin the dependent claims.

[0006] It is particularly advantageous that different types of headerdata with a shared signaling, depending on their signaling, are suppliedto a shared algorithm from the first group and the second group ofalgorithms. As a result, no additional signaling is required for suchheader data in order to assign the header data ahead of time to one ofthe two groups of algorithms in order then, based on the additionalsignaling, to select from the preselected group the algorithm to beexecuted so that the above-described savings in data quantity isachieved for the signaling.

[0007] It is also advantageous that the header data of at least tendifferent types can be signaled by means of a 3-bit signaling. This ispossible through the shared signaling of six of the ten different typesand achieves a savings of one bit in comparison to a separate signalingof each different type of header data.

DRAWINGS

[0008] An exemplary embodiment of the invention is shown in the drawingsand will be explained in detail in the description follows.

[0009]FIG. 1 shows a packet data unit with header data of a first type,

[0010]FIG. 2 shows a packet data unit with header data of a second type,

[0011]FIG. 3 shows a packet data unit with header data of a third type,

[0012]FIG. 4 shows a packet data unit with a preceding signaling, and

[0013]FIG. 5 shows a block circuit diagram of a receiver.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0014] In packet switched telecommunications networks, payload data 15according to FIG. 1 in the form of packet data units 1 are transmittedfrom a sender to a receiver 70 according to FIG. 5. The packet dataunits 1 pass through a number of protocol layers in the sender beforethey are finally sent. In the process, the individual protocol layersadd so-called protocol control data in the form of header data, whichare also referred to as “headers”, to the payload data 15. The headerdata are labeled with the reference numerals 5, 10 in FIG. 1 and,together with the payload data 15, comprise the packet data unit 1according to FIG. 1. In this connection, the header data 5, 10 are usedfor example to convey the packet data unit 1 with the payload data 15through the telecommunications network to the receiver 70. In order toreduce the data quantity of the header data 5, 10, compressionalgorithms in the sender are used. The header data 5, 10 are thencompressed with one of these compression algorithms and in this manner,are transmitted via the telecommunication network to the receiver 70 bymeans of the packet data unit 1. In the receiver 70, the header data 5,10 are then decompressed by means of a decompression algorithm, whichthen reverses the compression of the header data 5, 10 executed by thecompression algorithm used.

[0015] The IP protocol layer (Internet Protocol), which is introducedbelow by way of example, prepends a set of header data in the form of anIP header onto the data from higher protocol layers. If the data arereceived in the IP protocol layer from a higher TCP protocol layer(Transport Control Protocol), then these data can contain the payloaddata 15 and a prepended TCP header 10. The IP protocol layer then alsoprepends the IP header 5 onto the TCP header 10 so that an IP/TCP header5, 10 is generated, which is prepended onto the payload data 15according to FIG. 1. Correspondingly, an IP/UDP header 5, 20 (UDP=UserDataframe Protocol) is prepended onto the payload data 15 of the packetdata unit 1 if the data have been received in the IP protocol layer froma UDP protocol layer.

[0016] Compression algorithms in the sender are used to reduce the dataquantity of the header data 5, 10, 20. The compression of header data 5,10, 20, which are based on the Internet Protocol (IP), is described inreferences D2 and D3 and will be described briefly below in order toexplain the method according to the invention.

[0017] Reference D2 describes a method for compressing IP headers 5 incombination with TCP headers 10 or UDP headers 20. The method is basedon the single transmission of a complete combined IP/TCP header 5, 10 ofthis kind or of a complete IP/UDP header 5, 20, which is stored in acompressor of the sender and in a decompressor 45 of the receiver 70,under a particular identifier CID (Contest Identifier). In this case,the headers are naturally sent along with the corresponding packet dataunit 1. In the subsequent packet data units, those parts of the headerdata, which do not change or which constantly change, are then no longertransmitted with the header data 5, 10, 20. Parts of header data 5, 10,20 that change unpredictably are either transmitted to the receiver 70whole along with the corresponding associated packet data unit 1, oronly the changes in the header data 5, 10, 20 compared to the lastpacket data unit sent are transmitted to the receiver 70. The headerdata 5, 10, 20 stored in the decompressor 45 according to FIG. 5, underthe respectively associated identifier CID, are then updated orrefreshed based on the header data 5, 10, 20 received along with thesubsequently transmitted packet data units 1. In reference D2, thefollowing different types of header data 5, 10, 20 are defined:

[0018] 1. Regular header for uncompressed IP-based header data, forexample IP/TCP header data 5, 10 according to FIG. 1 or IP/UDP headerdata 5, 20 according to FIG. 2, which contain no othercompression-related data (type 1).

[0019] 2. Full header for uncompressed IP/TCP header data 5, 10 oruncompressed IP %UDP header data 5, 20 with additionalcompression-related data (type 2).

[0020] 3. Compressed_TCP for compressed IP/TCP header data according toFIG. 1 (type 3).

[0021] 4. Compressed_TCP_NON_DELTA for header data 5, 10, 20 in whichonly the data, which do not change or which constantly change, areomitted, but all other data are transmitted in a complete, compressedformat (type 4).

[0022] 5. Compressed_NON-TCP for compressed header data 5, 20, which arenot IP/TCP header data 5, 10, but in particular IP/UDP header data 5, 20according to FIG. 2 (type 5).

[0023] 6. Context_state for header data, which are sent back from thereceiver 70 to the sender or from the decompressor 45 to the compressoras an acknowledgment and for the synchronization of header data storedin the decompressor 45 and which do not play any role in the methodaccording to the invention (type 6).

[0024] Header data of type 1 are not compressed.

[0025] Header data of type to represent complete header data, which areto be stored in the decompressor 45, under the associated identifierCID.

[0026] Header data types 3, 4, and 5 are compressed header data, andheader data of type 6 are used for purposes of synchronizing the headerdata stored in the decompressor 45 and are sent from the decompressor 45of the receiver to the compressor of the sender.

[0027] The method described in reference D3 is based on the methoddescribed in D2, but is only used for packet data units 1 whose payloaddata 15 have had a set of RTP header data 25 according to FIG. 3prepended onto them in an RTP protocol layer (Real Time Protocol). Inthe subordinate UDP protocol layer, a UDP header 20 has also beenprepended onto the thus generated packet data unit. In the subordinateIP protocol layer, the packet data unit thus generated in the UDPprotocol layer has further IP header data 5 prepended onto it, thusgenerating the packet data unit 1 shown in FIG. 3. The header data 5,20, 25 shown there can also the referred to as IP/UDP/RTP header data.The following types of IP/UDP/RTP header data 5, 20, 25 can bedifferentiated:

[0028] 1. Regular header for uncompressed IP-based header data, forexample IP/TCP header data 5, 10 according to FIG. 1 or IP/UDP headerdata 5, 20 according to FIG. 2, which contain no othercompression-related data (type 7).

[0029] 2. Full header for uncompressed IP/TCP header data 5, 10 oruncompressed IP/UDP header data 5, 20 with additionalcompression-related data (type 8).

[0030] 3. Compressed_RTP for compressed IP/UDP/RTP header data 5, 20, 25(type 9).

[0031] 4. Compressed_UDP for header data in which only the IP/UDP header5, 20, but not the RTP header 25 have been compressed (type 10).

[0032] 5. Compressed_NON-TCP for compressed header data, which are notIP/UDP/RTP header data 5, 20, 25 (type 11).

[0033] 6. Context_state for header data, which are sent back from thereceiver 70 to the sender or from the decompressor 45 to the compressoras an acknowledgment and for the synchronization of header data storedin the decompressor 45 and which do not play any role in the methodaccording to the invention (type 12).

[0034] If packet data units 1 are transmitted from the sender thatcontains the compressor, to a receiver 70 that contains the decompressor45, then the decompressor 45 must be notified as to the nature or typeof header data that it is currently receiving. Usually a signaling 30,35, 40 is used for this, which is added or prepended onto the packetdata unit 1 to be transmitted, as shown in FIG. 4.

[0035] It is now conceivable for packet data units 1 to be transmittedto the receiver 70 with IP/TCP header data 510, IP/UDP header data 5,20, or IP/UDP/RTP header data 5, 20, 25. In order to permit anevaluation or decompression of header data of all of the types of headerdata that can be received in the decompressor 45, these types must bedifferentiated by means of the signaling 30, 35, 40. According to FIG.5, the decompressor 45 contains a first group 50 of algorithms forevaluating or decompressing header data of types 1 to 5 and a secondgroup 55 of algorithms for evaluating or decompressing header data oftypes 7 to 11. No algorithms need to be provided in the decompressor 45for header data of type 6 or type 12, since these header data are sentfrom the decompressor 45 of the receiver 70 to the compressor of thesender. Previously, 4 bits were required in order to be able toexplicitly signal the ten types of header data that can be evaluated ordecompressed in the decompressor 45; one bit was required to select thegroup 50, 55 of algorithms required for the evaluation or decompressionof the respective header data. The remaining three bits were used todifferentiate among five different algorithms in each of the two groups50, 55, in order to supply the five types of header data, which could beevaluated or decompressed in the corresponding group of algorithms, tothe correspondingly suitable algorithm for the evaluation ordecompression. Therefore, up till the present, four bits for thesignaling had to be transmitted along with each packet data unit 1.

[0036] The invention makes use of the fact that for the evaluation ordecompression of header data of types 1, 2, and 5, algorithms in thefirst group 50 of algorithms are provided, which correspond to therespective algorithm for evaluation or decompression of header data oftypes 7, 8, and 11 in the second group 55. This produces a third group60 in the decompressor 45, with algorithms, which can be used in ashared fashion for various types of header data, and consequentlyrepresents an intersection of the two groups 50, 55 of algorithms.Consequently, the third group 60 of shared algorithms includes a firstalgorithm for evaluating header data of type 1 and type 7, a secondalgorithm for evaluating header data of type 2 and type 8, and a thirdalgorithm for decompressing header data of type 5 and type 11. In thiscase, the remaining types of header data to be evaluated or decompressedin the manner described above, either by an algorithm from the firstgroup 50 of algorithms or by an algorithm from the second group 55 ofalgorithms. In this case, the header data of types 3 and 4 aredecompressed by means of a respective algorithm that is only containedin the first group 50 of algorithms, whereas header data of types 9 and10 are decompressed by means of a respective algorithm that is onlycontained in the second group 55 of algorithms.

[0037] In this manner, it is possible to respectively use a sharedsignaling for the types 1 and 7 of header data, for the types 2 and 8 ofheader data, and for the types 5 and 11 of header data so that a totalof three shared signalings and four additional signalings for the types3, 4, 9, and 10, or a total of seven different signalings are required,so that three bits are sufficient for the signaling. In FIGS. 4 and 5, afirst signaling bit is labeled with the reference numeral 30, a secondsignaling bit is labeled with the reference numeral 35, and a thirdsignaling bit is labeled with reference numeral 40.

[0038] This is particularly advantageous for telecommunication networksthat are embodied as mobile radio networks and in particular arerealized using the GSM standard (Global Systems for Mobilecommunications) or using the UMTS standard (Universal MobileTelecommunications System) and in which only a limited bandwidth or bitrate is available for the transmission of packet data units.

[0039] An evaluation of the signaling 30, 35, 40 takes place in thereceiver in a corresponding evaluation unit 65, which, depending on thesignaling detected, sends the received packet data unit 1 to either thefirst group 50, the second group 55, or the third group 60 of algorithmsfor evaluation or decompression.

[0040] A table is used below to give an example for the association ofthe signaling bits 30, 35, 40 with the individual types of header data:signaling bits type 30 35 40 type 1, type 7  0  0  0 type 2, type 8  0 0  1 type 5, type 11  0  1  0 type 3  0  1  1 type 4  1  0  0 type 9  1 0  1 type 10

1. A method for signaling various header data (5, 10, 20, 25) in thetransmission of packet data units (1) in a telecommunications networkdepending on a type of the respective header data (5, 10, 20, 25),wherein a set of header data (5, 10, 20, 25) received in a receiver (70)of the telecommunications network, depending on its signaling (30, 35,40), is supplied to one of at least two groups (50, 55) of algorithmsfor an evaluation, and wherein for a first type of header data (5, 10,20, 25), a first algorithm is provided in a first group (50) ofalgorithms, and for a second type of header data (5, 10, 20, 25) asecond algorithm is provided in a second group (55) of algorithms,wherein the first algorithm corresponds to the second algorithm,characterized in that the signaling (30, 35, 40) for the first type ofheader data (5, 10, 20, 25) and the signaling (30, 35, 40) for thesecond type of header data (5, 10, 20, 25) are combined into a sharedsignaling.
 2. The method according to claim 1, characterized in that thesignaling (30, 35, 40) is transmitted prepended onto the packet dataunit (1).
 3. The method according to claim 1 or 2, characterized in thatcompressed header data (5, 10, 20, 25) of various protocols with varioussignaling (30, 35, 40), depending on their signaling (30, 35, 40), aresupplied to an algorithm from one of the at least two groups (50, 55) ofalgorithms for decompression.
 4. The method according to claim 3,characterized in that compressed header data (5, 10, 20, 25) of anIP/TCP protocol (Internet Protocol)/(Transport Control Protocol),depending on their signaling (30, 35, 40), are supplied to an algorithmfrom the first group (50) of algorithms for decompression.
 5. The methodaccording to claim 3, characterized in that compressed header data (5,10, 20, 25) of an IP/UDP/RTP protocol (IP/User Dataframe Protocol/RealTime Protocol), depending on their signaling (30, 35, 40), are suppliedto an algorithm from the second group (55) of algorithms fordecompression.
 6. The method according to one of the preceding claims,characterized in that header data (5, 10, 20, 25) of various types withshared signaling, depending on their signaling (30, 35, 40), aresupplied to a shared algorithm from the first group (50) and secondgroup (55) of algorithms.
 7. The method according to claim 6,characterized in that uncompressed header data (5, 10, 20, 25) ofvarious types with shared signaling, depending on their signaling (30,35, 40), are supplied to a shared algorithm from the first group (50)and second group (55) of algorithms.
 8. The method according to claim 6or 7, characterized in that compressed header data (5, 10, 20, 25) ofvarious types with shared signaling, depending on their signaling (30,35, 40), are supplied to a shared algorithm from the first group (50)and second group (55) of algorithms for decompression.
 9. The methodaccording to claim 8, characterized in that compressed header data (5,10, 20, 25) of an IP/UDP protocol, depending on their signaling (30, 35,40), are supplied to a shared algorithm from the first group (50) andsecond group (55) of algorithms for decompression.
 10. The methodaccording to one of the preceding claims, characterized in that headerdata (5, 10, 20, 25) of at least ten different types are signaled bymeans of a 3-bit signaling (30, 35, 40).